crusade vs go to grass roots

crusade

verb
  • To make a grand concerted effort toward some purportedly worthy cause. 

  • To go on a military crusade. 

noun
  • A grand concerted effort toward some purportedly worthy cause. 

  • Any of the Papally-endorsed military expeditions undertaken by the Christians of Latin Europe in the 11th to 13th centuries to reconquer the Levant from the Muslims, as well as expeditions along the Baltic Sea and against the Cathars. 

  • Any war instigated and blessed by the Church for alleged religious ends, (especially) papal-sanctioned military campaigns against infidels or heretics. 

go to grass roots

How often have the words crusade and go to grass roots occurred in a corpus of books? (source: Google Ngram Viewer )